The invention relates to an apparatus for calibrating a pulse oximeter using a finger model approximated to a light-absorbing characteristic of a human finger.
Description of the Related Art
A pulse oximeter injects light rays of, e.g., two different wavelengths, each of which exhibits a different light-transmitting characteristic to oxygenated hemoglobin and reduced hemoglobin into the finger tip, etc., of a human being, calculates a ratio between variations of the transmitted light rays of the respective two wavelengths appearing as the arterial blood pulsates, and finds the degree of oxygen saturation of the circulating blood with this ratio as a function.
By the way, a method of calibrating this pulse oximeter has conventionally involved only the oximeter body, not including a measuring probe, and calibrations have been made electrically.
Another method calibrates the pulse oximeter by actually making a measurement on the finger tip of a healthy human being. The reliability of the calibration is judged by comparing such measurement with a plurality of measurements made with the finger tip of the same person installed to the measuring probe and then checking that the compared measurements are the same.
However, in the calibration method involving the actual measurement of the finger tip of a human being, the repetitivity of the measured value is so poor that it is difficult to judge whether the measured value is reliable or not.